When Neanderthal ancestors left Africa roughly 100,000 years earlier they adapted to the pathogens in their European environment, unlike modern humans who adapted to African pathogens. This transcontinental movement is known as the. If contact between humans and Neanderthals occurred in Europe and Asia the first contact may have been devastating to the Neanderthal population, because they would have had little if any immunity to the African pathogens. More recent historical events in Eurasia and the Americas show a similar pattern, where the unintentional introduction of viral, or bacterial pathogens to unprepared populations has led to mass mortality and local population extinction.
The most well-known example of this is the arrival ofto the New World, which brought and introduced foreign diseases when he and his crew arrived to a native population who had no immunity.
Anthropologist Pat Shipman, of Pennsylvania State University, suggested thatcould have played a role in Neanderthals’ extinction.
Polymorphism is common in nature; it is related to, and ; it usually functions to retain variety of form in a population living in a varied environment.
The most common example is, which occurs in many organisms. Other examples are mimetic forms of butterflies (see ), and human and .
According to the theory of evolution, polymorphism results from evolutionary processes, as does any aspect of a species. It isand is modified by . In , an individual’s genetic make-up allows for different morphs, and the switch mechanism that determines which morph is shown is environmental. In genetic polymorphism, the genetic make-up determines the morph. exhibit both types in a single population.